User Interface Design bullet Efficacy of User Interface Design Many technological innovations rely upon User Interface Design to elevate their technical complexity to a usable product. Technology alone may not win user acceptance and subsequent marketability. The User Experience, or how the user experiences the end product, is the key to acceptance. And that is where User Interface Design enters the design process. While product engineers focus on the technology, usability specialists focus on the user interface. For greatest efficiency and cost effectiveness, this working relationship should be maintained from the start of a project to its rollout.